Tunable Fabry-Perot filters and tunable vertical cavity surface emitting lasers (VCSEL's) have recently generated considerable interest in the art. Among other things, these devices are believed to have application for a wide range of different optical components and systems, e.g., wavelength division multiplexing (WDM) fiberoptic systems, switches, routers, etc.
In some tunable Fabry-Perot filters and in some tunable VCSEL's, tuning is achieved by using an electrostatic field to move a top mirror relative to a bottom mirror, whereby to change the length of the Fabry-Perot cavity and hence tune the wavelength of the device.
While such a construction is advantageous in that it provides a fast and easy way to tune the device, in practice it has proven difficult to produce relatively uniform devices. Significant performance variations typically occur from device-to-device and from batch-to-batch. In addition, significant performance variations can also occur with a specific device over time, as the device ages, changes temperature, etc.